In applications such as electronic transactions it may be required to verify that a computation (or program) has actually been executed on a specific processor, either by a user or by a third party. In “Controlled Physical Random Functions”, by Blaise Gassend and Dwaine Clarke and Marten van Dijk and Srinivas Devadas, Proceedings of the 18th Annual Computer Security Applications Conference, December, 2002 (further referred to as “prior art document”), certified execution is defined as a process that produces, together with the computation output, a certificate (called e-certificate) which proves to the user of a specific processor chip that a specific computation was carried out on that specific processor chip, and that the computation was executed and did produce the given computation output.